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Journal of Micro/Nanolithography, MEMS, and MOEMS

Study of CD variation caused by the black border effect and out-of-band radiation in extreme ultraviolet lithography
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Paper Abstract

Although extreme ultraviolet lithography (EUVL) remains a promising candidate for semiconductor device manufacturing of the 1× nm half pitch node and beyond, many technological burdens have to be overcome. The “field edge effect” in EUVL is one of them. The image border region of an EUV mask, also known as the “black border” (BB), reflects a few percent of the incident EUV light, resulting in a leakage of light into neighboring exposure fields, especially at the corner of the field where three adjacent exposures take place. This effect significantly impacts on critical dimension (CD) uniformity (CDU) across the exposure field. To avoid this phenomenon, a light-shielding border is introduced by etching away the entire absorber and multilayer at the image border region of the EUV mask. We present a method of modeling the field edge effect (also called the BB effect) by using rigorous lithography simulation with a calibrated resist model. An additional “flare level” at the field edge is introduced on top of the exposure tool flare map to account for the BB effect. The parameters in this model include the reflectivity and the width of the BB, which are mainly determining the leakage of EUV light and its influence range, respectively. Another parameter is the transition width which represents the half shadow effect of the reticle masking blades. By setting the corresponding parameters, the simulation results match well the experimental results obtained at the IMEC’s NXE:3100 EUV exposure tool. Moreover, these results indicate that the out-of-band (OoB) radiation also contributes to the CDU. Using simulation, we can also determine the OoB effect rigorously using the methodology of an “effective mask blank.” The study demonstrates that the impact of BB and OoB effects on CDU can be well predicted by simulations.

Paper Details

Date Published: 7 May 2014
PDF: 8 pages
J. Micro/Nanolith. MEMS MOEMS 13(2) 023005 doi: 10.1117/1.JMM.13.2.023005
Published in: Journal of Micro/Nanolithography, MEMS, and MOEMS Volume 13, Issue 2
Show Author Affiliations
Weimin Gao, Synopsys, Inc. (Belgium)
IMEC (Belgium)
Ardavan Niroomand, Micron Technology, Inc. (United States)
IMEC (Belgium)
Gian F. Lorusso, IMEC (Belgium)
Robert Boone, Synopsys, Inc. (United States)
Kevin Lucas, Synopsys, Inc. (United States)
Wolfgang Demmerle, Synopsys GmbH (Germany)

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